Systems and methods for treating cardiac arrhythmias

ABSTRACT

Systems and methods for treating cardiac arrhythmias are disclosed. In one embodiment, an SICD comprises two or more electrodes, a charge storage device, and a controller operatively coupled to two or more of the electrodes and the charge storage device. In some embodiments, the controller is configured to monitor cardiac activity of the heart of the patient, detect an occurrence of a cardiac arrhythmia based on the cardiac activity, and determine a type of the detected cardiac arrhythmia from two or more types of cardiac arrhythmias. If the determined type of cardiac arrhythmia is one of a first set of cardiac arrhythmia types, the controller sends an instruction for reception by an LCP to initiate the application of ATP therapy by the LCP. If the determined type of cardiac arrhythmia is not one of the first set cardiac arrhythmia types, the controller does not send the instruction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/113,173 filed on Feb. 6, 2015, the disclosuresof each incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to systems, devices, andmethods for treating cardiac arrhythmias, and more particularly, tosystems, devices, and methods for detecting cardiac arrhythmias andcoordinating therapy between multiple devices.

BACKGROUND

Pacing instruments can be used to treat patients suffering from variousheart conditions that result in a reduced ability of the heart todeliver sufficient amounts of blood to a patient's body. These heartconditions may lead to rapid, irregular, and/or inefficient heartcontractions. To help alleviate some of these conditions, variousdevices (e.g., pacemakers, defibrillators, etc.) have been implanted ina patient's body. Such devices may monitor and provide electricalstimulation to the heart to help the heart operate in a more normal,efficient and/or safe manner. In some cases, a patient may have multipleimplanted devices.

SUMMARY

The present disclosure generally relates to systems, devices, andmethods for treating cardiac arrhythmias, and more particularly, tosystems, devices, and methods for detecting cardiac arrhythmias andcoordinating treatment of anti-tachycardia pacing (ATP) therapy anddefibrillation shock therapy between a leadless cardiac pacemaker andanother medical device.

In one embodiment, a subcutaneous implantable cardioverter defibrillator(SICD) for delivering a defibrillation shock to a heart of a patientcomprises two or more electrodes, a charge storage device for storing acharge that can be delivered to shock the heart via two or more of theelectrodes, and a controller operatively coupled to two or more of theelectrodes and the charge storage device. The controller may beconfigured to monitor cardiac activity of the heart of the patient viacardiac signals received via two or more of the electrodes, detect anoccurrence of a cardiac arrhythmia based on the cardiac activity, anddetermine a type of the detected cardiac arrhythmia from two or moretypes of cardiac arrhythmias. If the determined type of cardiacarrhythmia is one of a first set of cardiac arrhythmia types, thecontroller may send an instruction via two or more of the electrodes forreception by a Leadless Cardiac Pacemaker (LCP) to initiate theapplication of ATP therapy by the LCP. If the determined type of cardiacarrhythmia is not one of the first set cardiac arrhythmia types, thecontroller may not send the instruction.

Additionally, or alternatively, in the previous embodiment, theinstruction may also include one or more ATP parameters that define oneor more characteristics of the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a method ofATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a number ofATP bursts applied during the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, thecontroller may further be configured to initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof a second set cardiac arrhythmia types, and wait to initiate chargingof the charge storage device if the determined type of the cardiacarrhythmia is one of the first set of cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, not initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof the first set of cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, terminate the charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof the second cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, thefirst set of type of cardiac arrhythmia types may include MonomorphicVentricular Tachycardia (MVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include one or more ofPolymorphic Ventricular Tachycardia (PVT), Supra Ventricular Tachycardia(SVT), and Ventricular Fibrillation (VF).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include PolymorphicVentricular Tachycardia (PVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include Supra VentricularTachycardia (SVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include MonomorphicVentricular Tachycardia (MVT).

Additionally, or alternatively, in any of the previous embodiments, thefirst set of cardiac arrhythmia types and the second set of cardiacarrhythmia types may share one or more common cardiac arrhythmia types,but this is not required.

Additionally, or alternatively, in any of the previous embodiments, thecardiac arrhythmia types in the first set of cardiac arrhythmia typesmay be user selectable.

Additionally, or alternatively, in any of the previous embodiments, theSICD may further comprise an energy storage module, and the cardiacarrhythmia types in the first set of cardiac arrhythmia types may dependat least partially on a charge level of the storage module.

Additionally, or alternatively, in any of the previous embodiments, todetermine a type of the detected cardiac arrhythmia from two or moretypes of cardiac arrhythmias, the controller may be configured tocompare the cardiac signals to one or more templates of cardiac signals.

In another embodiment, a subcutaneous implantable cardioverterdefibrillator (SICD) for delivering a defibrillation shock to a heart ofa patient may comprise two or more electrodes, a charge storage devicefor storing a charge that can be delivered to shock the heart via two ormore of the electrodes, and a controller operatively coupled to two ormore of the electrodes and the charge storage device. The controller maybe configured to monitor cardiac activity of the heart of the patientvia cardiac signals received via two or more of the electrodes, detectan occurrence of a cardiac arrhythmia based on the cardiac activity; anddetermine a type of the detected cardiac arrhythmia from two or moretypes of cardiac arrhythmias. If the determined type of cardiacarrhythmia is one of a first set of cardiac arrhythmia types, thecontroller may send an instruction via two or more of the electrodes forreception by a Leadless Cardiac Pacemaker (LCP) to initiate theapplication of ATP therapy by the LCP. If the determined type of cardiacarrhythmia is not one of the first set of cardiac arrhythmia types, thecontroller may not send the instruction.

Additionally, or alternatively, in the previous embodiment, theinstruction may also include one or more ATP parameters that define oneor more characteristics of the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a method ofATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a number ofATP bursts applied during the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, thecontroller may be further configured to initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof a second set of cardiac arrhythmia types, and wait to initiatecharging of the charge storage device if the determined type of thecardiac arrhythmia is not one of the second set of cardiac arrhythmiatypes.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, not initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof the first set of cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, terminate the charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof the second set of cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, thefirst set of cardiac arrhythmia types may include MonomorphicVentricular Tachycardia (MVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include one or more ofPolymorphic Ventricular Tachycardia (PVT), Supra Ventricular Tachycardia(SVT), and Ventricular Fibrillation (VF).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include PolymorphicVentricular Tachycardia (PVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include Supra VentricularTachycardia (SVT).

Additionally, or alternatively, in any of the previous embodiments, thesecond set of cardiac arrhythmia types may include MonomorphicVentricular Tachycardia (MVT).

Additionally, or alternatively, in any of the previous embodiments, thefirst set of cardiac arrhythmia types and the second set of cardiacarrhythmia types may share one or more common cardiac arrhythmia types,but this is not required.

In yet another embodiment, an implantable cardioverter defibrillator(ICD) for delivering a defibrillation shock to a heart of a patient maycomprise a charge storage device for storing a charge that can bedelivered to shock the heart and a controller operatively coupled to thecharge storage device. The controller may be configured to monitorcardiac activity of the heart of the patient, detect an occurrence of acardiac arrhythmia based on the cardiac activity, and determine a typeof the detected cardiac arrhythmia from two or more types of cardiacarrhythmias. If the determined type of cardiac arrhythmia is one of afirst set of cardiac arrhythmia types, the controller may be configuredto send an instruction for reception by a Leadless Cardiac Pacemaker(LCP) to initiate the application of ATP therapy by the LCP. If thedetermined type of cardiac arrhythmia is not one of the first set ofcardiac arrhythmia types, the controller may not send the instruction.

Additionally, or alternatively, in the previous embodiment, theinstruction may include one or more ATP parameters that define one ormore characteristics of the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a method ofATP therapy.

Additionally, or alternatively, in any of the previous embodiments, theone or more characteristics of the ATP therapy may comprise a number ofATP bursts applied during the ATP therapy.

Additionally, or alternatively, in any of the previous embodiments, thecontroller may be further configured to initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof a second set of cardiac arrhythmia types, and wait to initiatecharging of the charge storage device if the determined type of thecardiac arrhythmia is not one of the second set of cardiac arrhythmiatypes.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, not initiate charging of the chargestorage device if the determined type of the cardiac arrhythmia is thefirst set of cardiac arrhythmia types.

Additionally, or alternatively, in any of the previous embodiments, ifan instruction was sent to initiate the application of ATP therapy bythe LCP, the controller may be further configured to determine if theapplication of the ATP therapy by the LCP was successful in terminatingthe cardiac arrhythmia, and if so, terminate the charging of the chargestorage device if the determined type of the cardiac arrhythmia is oneof the second set of cardiac arrhythmia types.

In still another embodiment, a method implemented by an implantablecardioverter defibrillator (ICD) may comprise determining an occurrenceof a cardiac arrhythmia and determining a type of the detected cardiacarrhythmia from two or more types of cardiac arrhythmias. The method mayfurther comprise, if the determined type of cardiac arrhythmia is one ofa first set of cardiac arrhythmia types, sending an instruction forreception by a Leadless Cardiac Pacemaker (LCP) to initiate theapplication of ATP therapy by the LCP. Additionally, the method may alsocomprise, if the determined type of cardiac arrhythmia is not one of thefirst set of cardiac arrhythmia types, not sending the instruction tothe LCP.

Additionally, or alternatively, in the previous embodiment, the methodmay further comprise charging the charge storage device if thedetermined type of the cardiac arrhythmia is one of a second set ofcardiac arrhythmia types, and waiting to charge the charge storagedevice if the determined type of the cardiac arrhythmia is not one ofthe second set of cardiac arrhythmia types.

The above summary is not intended to describe each embodiment or everyimplementation of the present disclosure. Advantages and attainments,together with a more complete understanding of the disclosure, willbecome apparent and appreciated by referring to the followingdescription and claims taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing description of various illustrative embodiments in connectionwith the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of an illustrative leadless cardiacpacemaker (LCP) according to one embodiment of the present disclosure;

FIG. 2 is a schematic block diagram of another illustrative medicaldevice that may be used in conjunction with the LCP of FIG. 1;

FIG. 3 is a schematic diagram of an exemplary medical system thatincludes multiple LCPs and/or other devices in communication with oneanother

FIG. 4 is a schematic diagram of a system including an LCP and anothermedical device, in accordance with another embodiment of the presentdisclosure;

FIG. 5 is a schematic diagram of a system including a leadless cardiacpacemaker (LCP) and another medical device, in accordance with yetanother embodiment of the present disclosure;

FIG. 6 is a flow diagram of an illustrative method that may beimplemented by a medical device or medical device system, such as theillustrative medical devices and medical device systems described withrespect to FIGS. 1-5;

FIG. 7 is a flow diagram of an illustrative method that may beimplemented by a medical device or medical device system, such as theillustrative medical devices and medical device systems described withrespect to FIGS. 1-5; and

FIG. 8 is a flow diagram of an illustrative method that may beimplemented by a medical device or medical device system, such as theillustrative medical devices and medical device systems described withrespect to FIGS. 1-5.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way ofembodiment in the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspects of thedisclosure to the particular illustrative embodiments described. On thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

The following description should be read with reference to the drawingsin which similar elements in different drawings are numbered the same.The description and the drawings, which are not necessarily to scale,depict illustrative embodiments and are not intended to limit the scopeof the disclosure.

This disclosure describes systems, devices, and methods for detectingand treating cardiac arrhythmias, and more particularly, to systems,devices, and methods implementing different treatment protocols fordifferent types of arrhythmias. One option for treatingtachyarrhythmias, one type of cardiac arrhythmia, includes usinganti-tachycardia therapy (ATP) techniques. Some embodiments of thesetechniques include delivering pacing pulses to the heart of the patientat a faster rate than the tachycardia in an effort to get the heart totrack the ATP pulses, thereby terminating the physiologically inducedtachycardia. If ATP therapy does not work, then other measures, such asdelivering a defibrillation pulse to the heart may be employed toattempt to terminate the tachycardia. Tachycardias may be classifiedinto a number of different types of tachycardias—including monomorphicventricular tachycardia (MVT), polymorphic ventricular tachycardia(PVT), supra-ventricular tachycardia (SVT) and Ventricular Fibrillation(VF). ATP therapy may be more likely to be effective at terminating someof these tachycardias than other of these tachycardias. For example, ATPmay be most effective at terminating MVT (perhaps 80-90% termination).Efficacy may decrease for PVT (e.g. e.g. 20-40% termination), and SVTand VF (10-20% termination). Moreover, applying ATP therapy to onlycertain well-suited tachyarrhythmias may help reduce acceleration ofother less-suited tachyarrhythmias into the defibrillation/cardioversionzone. Accordingly, it may be beneficial to employ different therapyprotocols for different types of tachycardias, as will be more fullydetailed below.

FIG. 1 is a conceptual drawing of an exemplary leadless cardiacpacemaker (LCP) that may be implanted into a patient and may operate tosense physiological signals and parameters and deliver one or more typesof electrical stimulation therapy to tissues of the patient. Exampleelectrical stimulation therapy includes bradycardia pacing, rateresponsive pacing therapy, cardiac resynchronization therapy (CRT),anti-tachycardia pacing (ATP) therapy and/or the like. As can be seen inFIG. 1, LCP 100 may be a compact device with all components housedwithin LCP 100 or directly on housing 120. LCP 100 may includecommunication module 102, pulse generator module 104, electrical sensingmodule 106, mechanical sensing module 108, processing module 110, energystorage module 112, and electrodes 114.

As depicted in FIG. 1, LCP 100 may include electrodes 114, which can besecured relative to housing 120 and electrically exposed to tissueand/or blood surrounding LCP 100. Electrodes 114 may generally conductelectrical signals to and from LCP 100 and the surrounding tissue and/orblood. Such electrical signals can include communication pulses,electrical stimulation pulses, and intrinsic cardiac electrical signals,to name a few. Intrinsic cardiac electrical signals may includeelectrical signals generated by the heart and may be represented by anelectrocardiogram (ECG).

Electrodes 114 may include one or more biocompatible conductivematerials such as various metals or alloys that are known to be safe forimplantation within a human body. In some instances, electrodes 114 maybe generally disposed on either end of LCP 100 and may be in electricalcommunication with one or more of modules 102, 104, 106, 108, and 110.In embodiments where electrodes 114 are secured directly to housing 120,an insulative material may electrically isolate the electrodes 114 fromadjacent electrodes, housing 120, and/or other parts of LCP 100. In someinstances, some or all of electrodes 114 may be spaced from housing 120and connected to housing 120 and/or other components of LCP 100 throughconnecting wires. In such instances, the electrodes 114 may be placed ona tail (not shown) that extends out away from the housing 120. As shownin FIG. 1, in some embodiments, LCP 100 may include electrodes 114′.Electrodes 114′ may be in addition to electrodes 114, or may replace oneor more of electrodes 114. Electrodes 114′ may be similar to electrodes114 except that electrodes 114′ are disposed on the sides of LCP 100. Insome cases, electrodes 114′ may increase the number of electrodes bywhich LCP 100 may deliver communication pulses and/or electricalstimulation pulses, and/or may sense intrinsic cardiac electricalsignals, communication pulses, and/or electrical stimulation pulses.

Electrodes 114 and/or 114′ may assume any of a variety of sizes and/orshapes, and may be spaced at any of a variety of spacings. For example,electrodes 114 may have an outer diameter of two to twenty millimeters(mm). In other embodiments, electrodes 114 and/or 114′ may have adiameter of two, three, five, seven millimeters (mm), or any othersuitable diameter, dimension and/or shape. Example lengths forelectrodes 114 and/or 114′ may include, for example, one, three, five,ten millimeters (mm), or any other suitable length. As used herein, thelength is a dimension of electrodes 114 and/or 114′ that extends awayfrom the outer surface of the housing 120. In some instances, at leastsome of electrodes 114 and/or 114′ may be spaced from one another by adistance of twenty, thirty, forty, fifty millimeters (mm), or any othersuitable spacing. The electrodes 114 and/or 114′ of a single device mayhave different sizes with respect to each other, and the spacing and/orlengths of the electrodes on the device may or may not be uniform.

In the embodiment shown, communication module 102 may be electricallycoupled to electrodes 114 and/or 114′ and may be configured to delivercommunication pulses to tissues of the patient for communicating withother devices such as sensors, programmers, other medical devices,and/or the like. Communication pulses, as used herein, may be anymodulated signal that conveys information to another device, either byitself or in conjunction with one or more other modulated signals. Insome embodiments, communication pulses may be limited to sub-thresholdsignals that do not result in capture of the heart yet still conveyinformation. The communication pulses may be delivered to another devicethat is located either external or internal to the patient's body.Communication module 102 may additionally be configured to sense forcommunication pulses delivered by other devices, which may be locatedexternal or internal to the patient's body.

Communication module 102 may communicate to help accomplish one or moredesired functions. Some example functions include delivering senseddata, using communicated data for determining occurrences of events suchas arrhythmias, coordinating delivery of electrical stimulation therapy,and/or other functions. In some cases, LCP 100 may use communicationpulses to communicate raw information, processed information, messagesand/or commands, and/or other data. Raw information may includeinformation such as sensed electrical signals (e.g. a sensed ECG),signals gathered from coupled sensors, and the like. In someembodiments, the processed information may include signals that havebeen filtered using one or more signal processing techniques. Processedinformation may also include parameters and/or events that aredetermined by the LCP 100 and/or another device, such as a determinedheart rate, timing of determined heartbeats, timing of other determinedevents, determinations of threshold crossings, expirations of monitoredtime periods, activity level parameters, blood-oxygen parameters, bloodpressure parameters, heart sound parameters, and the like. Messagesand/or commands may include instructions or the like directing anotherdevice to take action, notifications of imminent actions of the sendingdevice, requests for reading from the receiving device, requests forwriting data to the receiving device, information messages, and/or othermessages commands.

In at least some embodiments, communication module 102 (or LCP 100) mayfurther include switching circuitry to selectively connect one or moreof electrodes 114 and/or 114′ to communication module 102 in order toselect which electrodes 114 and/or 114′ that communication module 102delivers communication pulses. It is contemplated that communicationmodule 102 may communicating with other devices via conducted signals,radio frequency (RF) signals, optical signals, acoustic signals,inductive coupling, and/or any other suitable communication methodology.

In the embodiment shown, a pulse generator module 104 may beelectrically connected to one or more of electrodes 114 and/or 114′.Pulse generator module 104 may be configured to generate electricalstimulation pulses and deliver the electrical stimulation pulses totissues of a patient via one or more of the electrodes 114 and/or 114′in order to effectuate one or more electrical stimulation therapies.Electrical stimulation pulses as used herein are meant to encompass anyelectrical signals that may be delivered to tissue of a patient forpurposes of treatment of any type of disease or abnormality. Forexample, when used to treat heart disease, the pulse generator module104 may generate electrical stimulation pacing pulses for capturing theheart of the patient, i.e. causing the heart to contract in response tothe delivered electrical stimulation pulse. In another embodiment, theelectrical stimulation pulses may be defibrillation/cardioversion pulsesfor shocking the heart out of fibrillation. In yet another embodiment,the electrical stimulation pulses may be anti-tachycardia pacing (ATP)pulses. These are just some examples. When used to treat other ailments,the pulse generator module 104 may generate electrical stimulationpulses suitable for neurostimulation therapy or the like. Pulsegenerator module 104 may include one or more capacitor elements and/orother charge storage devices to aid in generating and deliveringappropriate electrical stimulation pulses. In the embodiment shown,pulse generator module 104 may use energy stored in energy storagemodule 112 to generate the electrical stimulation pulses.

Pulse generator module 104 may include the capability to modify theelectrical stimulation pulses, such as by adjusting the pulse widthand/or amplitude of the electrical stimulation pulses. When pacing theheart, this may help tailor the electrical stimulation pulses to capturethe heart a particular patient, sometimes with reduced battery usage.For neurostimulation therapy, adjusting the pulse width and/or amplitudemay help tailor the therapy for a particular application and/or helpmake the therapy more effective for a particular patient.

In some embodiments, LCP 100 may include an electrical sensing module106 and mechanical sensing module 108. Electrical sensing module 106 maybe configured to sense intrinsic cardiac electrical signals conductedfrom electrodes 114 and/or 114′ to electrical sensing module 106. Forexample, electrical sensing module 106 may be electrically connected toone or more electrodes 114 and/or 114′ and electrical sensing module 106may be configured to receive cardiac electrical signals conductedthrough electrodes 114 and/or 114′. In some embodiments, the cardiacelectrical signals may represent local information from the chamber inwhich LCP 100 is implanted. For instance, if LCP 100 is implanted withina ventricle of the heart, cardiac electrical signals sensed by LCP 100through electrodes 114 and/or 114′ may represent ventricular cardiacelectrical signals. Mechanical sensing module 108 may include, or beelectrically connected to, various sensors, such as accelerometers,blood pressure sensors, heart sound sensors, blood-oxygen sensors,and/or other sensors which measure one or more physiological parametersof the heart and/or patient. Mechanical sensing module 108, whenpresent, may gather signals from the sensors indicative of the variousphysiological parameters. Both electrical sensing module 106 andmechanical sensing module 108 may be connected to processing module 110and may provide signals representative of the sensed cardiac electricalsignals and/or physiological signals to processing module 110. Althoughdescribed with respect to FIG. 1 as separate sensing modules, in someembodiments, electrical sensing module 106 and mechanical sensing module108 may be combined into a single module.

Processing module 110 may be configured to control the operation of LCP100. For example, processing module 110 may be configured to receivecardiac electrical signals from electrical sensing module 106 and/orphysiological signals from mechanical sensing module 108. Based on thereceived signals, processing module 110 may determine, for example,occurrences and types of arrhythmias. Processing module 110 may furtherreceive information from communication module 102. In some embodiments,processing module 110 may additionally use such received information todetermine occurrences and types of arrhythmias. However, in otherembodiments, LCP 100 may use the received information instead of thesignals received from electrical sensing module 106 and/or mechanicalsensing module 108—for instance if the received information is moreaccurate than the signals received from electrical sensing module 106and/or mechanical sensing module 108 or if electrical sensing module 106and/or mechanical sensing module 108 have been disabled or omitted fromLCP 100.

Based on a determined arrhythmia, processing module 110 may controlpulse generator module 104 to generate electrical stimulation pulses inaccordance with one or more electrical stimulation therapies to treatthe determined arrhythmia. For example, processing module 110 maycontrol pulse generator module 104 to generate pacing pulses withvarying parameters and in different sequences to effectuate one or moreelectrical stimulation therapies. For example, in controlling pulsegenerator module 104 to deliver bradycardia pacing therapy, processingmodule 110 may control pulse generator module 104 to deliver pacingpulses designed to capture the heart of the patient at a regularinterval to help prevent the heart of a patient from falling below apredetermined threshold. In some cases, the rate of pacing may beincreased with an increased activity level of the patient (e.g. rateadaptive pacing). For ATP therapy, processing module 110 may controlpulse generator module 104 to deliver pacing pulses at a rate fasterthan an intrinsic heart rate of a patient in attempt to force the heartto beat in response to the delivered pacing pulses rather than inresponse to intrinsic cardiac electrical signals. Once the heart isfollowing the pacing pulses, processing module 110 may control pulsegenerator module 104 to reduce the rate of delivered pacing pulses downto a safer level. In CRT, processing module 110 may control pulsegenerator module 104 to deliver pacing pulses in coordination withanother device to cause the heart to contract more efficiently. In caseswhere pulse generator module 104 is capable of generating defibrillationand/or cardioversion pulses for defibrillation/cardioversion therapy,processing module 110 may control pulse generator module 104 to generatesuch defibrillation and/or cardioversion pulses. In some cases,processing module 110 may control pulse generator module 104 to generateelectrical stimulation pulses to provide electrical stimulationtherapies different than those examples described above.

Aside from controlling pulse generator module 104 to generate differenttypes of electrical stimulation pulses and in different sequences, insome embodiments, processing module 110 may also control pulse generatormodule 104 to generate the various electrical stimulation pulses withvarying pulse parameters. For example, each electrical stimulation pulsemay have a pulse width and a pulse amplitude. Processing module 110 maycontrol pulse generator module 104 to generate the various electricalstimulation pulses with specific pulse widths and pulse amplitudes. Forexample, processing module 110 may cause pulse generator module 104 toadjust the pulse width and/or the pulse amplitude of electricalstimulation pulses if the electrical stimulation pulses are noteffectively capturing the heart. Such control of the specific parametersof the various electrical stimulation pulses may help LCP 100 providemore effective delivery of electrical stimulation therapy.

In some embodiments, processing module 110 may further controlcommunication module 102 to send information to other devices. Forexample, processing module 110 may control communication module 102 togenerate one or more communication pulses for communicating with otherdevices of a system of devices. For instance, processing module 110 maycontrol communication module 102 to generate communication pulses inparticular sequences, where the specific sequences convey differentinformation. Communication module 102 may also receive communicationsignals for potential action by processing module 110.

In further embodiments, processing module 110 may control switchingcircuitry by which communication module 102 and pulse generator module104 deliver communication pulses and/or electrical stimulation pulses totissue of the patient. As described above, both communication module 102and pulse generator module 104 may include circuitry for connecting oneor more electrodes 114 and/114′ to communication module 102 and/or pulsegenerator module 104 so those modules may deliver the communicationpulses and electrical stimulation pulses to tissue of the patient. Thespecific combination of one or more electrodes by which communicationmodule 102 and/or pulse generator module 104 deliver communicationpulses and electrical stimulation pulses may influence the reception ofcommunication pulses and/or the effectiveness of electrical stimulationpulses. Although it was described that each of communication module 102and pulse generator module 104 may include switching circuitry, in someembodiments, LCP 100 may have a single switching module connected to thecommunication module 102, the pulse generator module 104, and electrodes114 and/or 114′. In such embodiments, processing module 110 may controlthe switching module to connect modules 102/104 and electrodes 114/114′as appropriate.

In some embodiments, processing module 110 may include a pre-programmedchip, such as a very-large-scale integration (VLSI) chip or anapplication specific integrated circuit (ASIC). In such embodiments, thechip may be pre-programmed with control logic in order to control theoperation of LCP 100. By using a pre-programmed chip, processing module110 may use less power than other programmable circuits while able tomaintain basic functionality, thereby potentially increasing the batterylife of LCP 100. In other instances, processing module 110 may include aprogrammable microprocessor or the like. Such a programmablemicroprocessor may allow a user to adjust the control logic of LCP 100after manufacture, thereby allowing for greater flexibility of LCP 100than when using a pre-programmed chip.

Processing module 110, in additional embodiments, may include a memorycircuit and processing module 110 may store information on and readinformation from the memory circuit. In other embodiments, LCP 100 mayinclude a separate memory circuit (not shown) that is in communicationwith processing module 110, such that processing module 110 may read andwrite information to and from the separate memory circuit. The memorycircuit, whether part of processing module 110 or separate fromprocessing module 110, may be volatile memory, non-volatile memory, or acombination of volatile memory and non-volatile memory.

Energy storage module 112 may provide a power source to LCP 100 for itsoperations. In some embodiments, energy storage module 112 may be anon-rechargeable lithium-based battery. In other embodiments, thenon-rechargeable battery may be made from other suitable materials. Insome embodiments, energy storage module 112 may include a rechargeablebattery. In still other embodiments, energy storage module 112 mayinclude other types of energy storage devices such as super capacitors.

To implant LCP 100 inside a patient's body, an operator (e.g., aphysician, clinician, etc.), may fix LCP 100 to the cardiac tissue ofthe patient's heart. To facilitate fixation, LCP 100 may include one ormore anchors 116. Anchor 116 may include any number of fixation oranchoring mechanisms. For example, anchor 116 may include one or morepins, staples, threads, screws, helix, tines, and/or the like. In someembodiments, although not shown, anchor 116 may include threads on itsexternal surface that may run along at least a partial length of anchor116. The threads may provide friction between the cardiac tissue and theanchor to help fix anchor 116 within the cardiac tissue. In otherembodiments, anchor 116 may include other structures such as barbs,spikes, or the like to facilitate engagement with the surroundingcardiac tissue.

FIG. 2 depicts an embodiment of another medical device (MD) 200, whichmay operate to sense physiological signals and/or parameters and deliverone or more types of electrical stimulation therapy to tissues of thepatient. In the embodiment shown, MD 200 may include a communicationmodule 202, a pulse generator module 204, an electrical sensing module206, a mechanical sensing module 208, a processing module 210, and anenergy storage module 218. Each of modules 202, 204, 206, 208, and 210may be similar to modules 102, 104, 106, 108, and 110 of LCP 100.Additionally, energy storage module 218 may be similar to energy storagemodule 112 of LCP 100. In some embodiments, however, MD 200 may have alarger volume within housing 220. In such embodiments, MD 200 mayinclude a larger energy storage module 218 and/or a larger processingmodule 210 capable of handling more complex operations than processingmodule 110 of LCP 100.

While MD 200 may be another leadless device such as shown in FIG. 1, insome instances MD 200 may include leads, such as leads 212. Leads 212may include electrical wires that conduct electrical signals betweenelectrodes 214 and one or more modules located within housing 220. Insome cases, leads 212 may be connected to and extend away from housing220 of MD 200. In some embodiments, leads 212 are implanted on, within,or adjacent to a heart of a patient. Leads 212 may contain one or moreelectrodes 214 positioned at various locations on leads 212 and variousdistances from housing 220. Some leads 212 may only include a singleelectrode 214, while other leads 212 may include multiple electrodes214. Generally, electrodes 214 are positioned on leads 212 such thatwhen leads 212 are implanted within the patient, one or more of theelectrodes 214 are positioned to perform a desired function. In somecases, the one or more of the electrodes 214 may be in contact with thepatient's cardiac tissue. In other cases, the one or more of theelectrodes 214 may be positioned subcutaneously but adjacent thepatient's heart. The electrodes 214 may conduct intrinsically generatedelectrical cardiac signals to leads 212. Leads 212 may, in turn, conductthe received electrical cardiac signals to one or more of the modules202, 204, 206, and 208 of MD 200. In some cases, MD 200 may generateelectrical stimulation signals, and leads 212 may conduct the generatedelectrical stimulation signals to electrodes 214. Electrodes 214 maythen conduct the electrical stimulation signals to the cardiac tissue ofthe patient (either directly or indirectly). MD 200 may also include oneor more electrodes 214 not disposed on a lead 212. For example, one ormore electrodes 214 may be connected directly to housing 220.

Leads 212, in some embodiments, may additionally contain one or moresensors, such as accelerometers, blood pressure sensors, heart soundsensors, blood-oxygen sensors, and/or other sensors which are configuredto measure one or more physiological parameters of the heart and/orpatient. In such embodiments, mechanical sensing module 208 may be inelectrical communication with leads 212 and may receive signalsgenerated from such sensors.

While not required, in some embodiments MD 200 may be an implantablemedical device. In such embodiments, housing 220 of MD 200 may beimplanted in, for example, a transthoracic region of the patient.Housing 220 may generally include any of a number of known materialsthat are safe for implantation in a human body and may, when implanted,hermetically seal the various components of MD 200 from fluids andtissues of the patient's body. In such embodiments, leads 212 may beimplanted at one or more various locations within the patient, such aswithin the heart of the patient, adjacent to the heart of the patient,adjacent to the spine of the patient, or any other desired location.

In some embodiments, MD 200 may be an implantable cardiac pacemaker(ICP). In these embodiments, MD 200 may have one or more leads, forexample leads 212, which are implanted on or within the patient's heart.The one or more leads 212 may include one or more electrodes 214 thatare in contact with cardiac tissue and/or blood of the patient's heart.MD 200 may be configured to sense intrinsically generated cardiacelectrical signals and determine, for example, one or more cardiacarrhythmias based on analysis of the sensed signals. MD 200 may beconfigured to deliver CRT, ATP therapy, bradycardia therapy, and/orother therapy types via leads 212 implanted within the heart. In someembodiments, MD 200 may additionally be configured to providedefibrillation/cardioversion therapy.

In some instances, MD 200 may be an implantablecardioverter-defibrillator (ICD). In such embodiments, MD 200 mayinclude one or more leads implanted within a patient's heart. MD 200 mayalso be configured to sense electrical cardiac signals, determineoccurrences of tachyarrhythmias based on the sensed electrical cardiacsignals, and deliver defibrillation and/or cardioversion therapy inresponse to determining an occurrence of a tachyarrhythmia (for exampleby delivering defibrillation and/or cardioversion pulses to the heart ofthe patient). In other embodiments, MD 200 may be a subcutaneousimplantable cardioverter-defibrillator (SICD). In embodiments where MD200 is an SICD, one of leads 212 may be a subcutaneously implanted lead.In at least some embodiments where MD 200 is an SICD, MD 200 may includeonly a single lead which is implanted subcutaneously but outside of thechest cavity, however this is not required.

In some embodiments, MD 200 may not be an implantable medical device.Rather, MD 200 may be a device external to the patient's body, andelectrodes 214 may be skin-electrodes that are placed on a patient'sbody. In such embodiments, MD 200 may be able to sense surfaceelectrical signals (e.g. electrical cardiac signals that are generatedby the heart or electrical signals generated by a device implantedwithin a patient's body and conducted through the body to the skin). Insuch embodiments, MD 200 may be configured to deliver various types ofelectrical stimulation therapy, including, for example, defibrillationtherapy.

FIG. 3 illustrates an embodiment of a medical device system and acommunication pathway through which multiple medical devices 302, 304,306, and/or 310 of the medical device system may communicate. In theembodiment shown, medical device system 300 may include LCPs 302 and304, external medical device 306, and other sensors/devices 310.External device 306 may be a device disposed external to a patient'sbody, as described previously with respect to MD 200. Othersensors/devices 310 may be any of the devices described previously withrespect to MD 200, such as ICPs, ICDs, and SICDs. Other sensors/devices310 may also include various diagnostic sensors that gather informationabout the patient, such as accelerometers, blood pressure sensors, orthe like. In some cases, other sensors/devices 310 may include anexternal programmer device that may be used to program one or moredevices of system 300.

Various devices of system 300 may communicate via communication pathway308. For example, LCPs 302 and/or 304 may sense intrinsic cardiacelectrical signals and may communicate such signals to one or more otherdevices 302/304, 306, and 310 of system 300 via communication pathway308. In one embodiment, one or more of devices 302/304 may receive suchsignals and, based on the received signals, determine an occurrence ofan arrhythmia. In some cases, device or devices 302/304 may communicatesuch determinations to one or more other devices 306 and 310 of system300. In some cases, one or more of devices 302/304, 306, and 310 ofsystem 300 may take action based on the communicated determination of anarrhythmia, such as by delivering a suitable electrical stimulation tothe heart of the patient. One or more of devices 302/304, 306, and 310of system 300 may additionally communicate command or response messagesvia communication pathway. The command messages may cause a receivingdevice to take a particular action whereas response messages may includerequested information or a confirmation that a receiving device did, infact, receive a communicated message or data.

It is contemplated that the various devices of system 300 maycommunicate via pathway 308 using conducted signals, RF signals,inductive coupling, optical signals, acoustic signals, or any othersignals suitable for communication. In some instances, the variousdevices of system 300 may communicate via pathway 308 using differentsignal types. For instance, other sensors/device 310 may communicatewith external device 306 using a first signal type (e.g. RFcommunication) but communicate with LCPs 302/304 using a second signaltype (e.g. conducted communication). Further, in some embodiments,communication between devices may be limited. For instance, as describedabove, in some embodiments, LCPs 302/304 may communicate with externaldevice 306 only through other sensors/devices 310, where LCPs 302/304send signals to other sensors/devices 310, and other sensors/devices 310relay the received signals to external device 306. This is just oneexample.

In some cases, the various devices of system 300 may communicate viapathway 308 using conducted communication signals. Accordingly, devicesof system 300 may have components that allow for such conductedcommunication. For instance, the devices of system 300 may be configuredto transmit conducted communication signals (e.g. current and/or voltagepulses) into the patient's body via one or more electrodes of atransmitting device, and may receive the conducted communication signals(e.g. pulses) via one or more electrodes of a receiving device. Thepatient's body may “conduct” the conducted communication signals (e.g.pulses) from the one or more electrodes of the transmitting device tothe electrodes of the receiving device in the system 300. In suchembodiments, the delivered conducted communication signals (e.g. pulses)may differ from pacing pulses, defibrillation and/or cardioversionpulses, or other electrical stimulation therapy signals. For example,the devices of system 300 may deliver electrical communication pulses atan amplitude/pulse width that is sub-threshold (e.g. does not capturethe heart, phrenic nerve, and/or other tissue). Although, in some cases,the amplitude/pulse width of the delivered electrical communicationpulses may be above a capture threshold, but may be delivered during anirrelevant time period. For example, the amplitude/pulse width of thedelivered electrical communication pulses may be above a capturethreshold of the heart, but may be delivered during a refractory periodof the heart and/or may be incorporated in or modulated onto a pacingpulse, as desired.

Delivered electrical communication pulses may be modulated in anysuitable manner to encode communicated information. In some cases, thecommunication pulses may be pulse width modulated and/or amplitudemodulated. Alternatively, or in addition, the time between pulses may bemodulated to encode desired information. In some cases, conductedcommunication pulses may be voltage pulses, current pulses, biphasicvoltage pulses, biphasic current pulses, or any other suitableelectrical pulse as desired.

FIGS. 4 and 5 show illustrative medical device systems that may beconfigured to operate according to techniques disclosed herein. Forexample, the systems may include multiple devices that are implantedwithin a patient and are configured to sense physiological signals,determine occurrences of cardiac arrhythmias, and deliver electricalstimulation to treat detected cardiac arrhythmias. In FIG. 4, an LCP 402is shown fixed to the interior of the right ventricle of the heart 410,and a pulse generator 406 is shown coupled to a lead 412 having one ormore electrodes 408 a-408 c. In some cases, the pulse generator 406 maybe part of a subcutaneous implantable cardioverter-defibrillator (SICD),and the one or more electrodes 408 a-408 c may be positionedsubcutaneously adjacent the heart. LCP 402 may communicate with theSICD, such as via communication pathway 308. The locations of LCP 402,pulse generator 406, lead 412, and electrodes 408 a-c depicted in FIG. 4are just exemplary. In other embodiments of system 400, LCP 402 may bepositioned in the left ventricle, right atrium, or left atrium of theheart, as desired. In still other embodiments, LCP 402 may be implantedexternally adjacent to heart 410 or even remote from heart 410.

In FIG. 5, an LCP 502 is shown fixed to the interior of the leftventricle of the heart 510, and a pulse generator 506 is shown coupledto a lead 512 having one or more electrodes 504 a-504 c. In some cases,the pulse generator 506 may be part of an implantable cardiac pacemaker(ICP) and/or an implantable cardioverter-defibrillator (ICD), and theone or more electrodes 504 a-504 c may be positioned in the heart 510.In some cases, LCP 502 may communicate with the implantable cardiacpacemaker (ICP) and/or an implantable cardioverter-defibrillator (ICD),such as via communication pathway 308. As with FIG. 4, the locations ofLCP 502, pulse generator 506, lead 512, and electrodes 504 a-c depictedin FIG. 5 are just exemplary. In other embodiments of system 500, LCP502 may be positioned in the right ventricle, right atrium, or leftatrium of the heart, as desired. In still other embodiments, LCP 502 maybe implanted externally adjacent to heart 510 or even remote from heart510. Additionally, in some embodiments lead 512 and/or electrodes 504a-c may be disposed in different chambers of heart 510, or pulsegenerator may include additional leads and/or electrodes that aredisposed within or adjacent to heart 510.

The medical device systems 400 and 500 may also include an externalsupport device, such as external support devices 420 and 520. Externalsupport devices 420 and 520 can be used to perform functions such asdevice identification, device programming and/or transfer of real-timeand/or stored data between devices using one or more of thecommunication techniques described herein. As one embodiment,communication between external support device 420 and the pulsegenerator 406 is performed via a wireless mode, and communicationbetween the pulse generator 406 and LCP 402 is performed via a conductedmode. In some embodiments, communication between the LCP 402 andexternal support device 420 is accomplished by sending communicationinformation through the pulse generator 406. However, in otherembodiments, communication between the LCP 402 and external supportdevice 420 may be via a communication module.

FIGS. 4-5 only illustrate a few embodiments of medical device systemsthat may be configured to operate according to techniques disclosedherein. Other example medical device systems may include additional ordifferent medical devices and/or configurations. For instance, othermedical device systems that are suitable to operate according totechniques disclosed herein may include additional LCPs implanted withinthe heart. Another example medical device system may include a pluralityof LCPs with or without other devices such as pulse generator 406 or506, with at least one LCP capable of delivering defibrillation therapy.Still another embodiment may include one or more LCPs implanted alongwith a transvenous pacemaker and with or without an implanted SICD. Inyet other embodiments, the configuration or placement of the medicaldevices, leads, and/or electrodes may be different from those depictedin FIGS. 4 and 5. Accordingly, it should be recognized that numerousother medical device systems, different from those illustrated in FIGS.4 and 5, may be operated in accordance with techniques disclosed herein.The embodiments systems shown in FIGS. 4 and 5 should not be viewed aslimiting.

Using the system of FIG. 4 as one example, LCP 402 and the ICD (whichcan be a non-subcutaneously implanted device, or a subcutaneouslyimplanted device—an SICD), which can include pulse generator 406, maydetermine occurrences of cardiac arrhythmias and discriminate betweendifferent types of cardiac arrhythmias. In some embodiments, the typesof cardiac arrhythmias include tachyarrhythmias, and the ICD may furtheridentify occurrences of tachyarrhythmias as specific types oftachyarrhythmias. As used herein, the term tachyarrhythmia may includeventricular fibrillation (VF). Based on the determined type oftachyarrhythmia, LCP 402 and/or the ICD may implement differingtreatment protocols. By tailoring the specific treatment protocol to thedifferent types of tachyarrhythmias, the system of LCP 402 and the ICDmay more effectively conserve battery life and/or reduce the amount ofunnecessary defibrillation and/or cardioversion pulses delivered to thepatient—which can be a painful and scary experience for the patient.

In some embodiments, the ICD may operate to determine occurrences oftachyarrhythmias and types of tachyarrhythmias in accordance with theillustrative flow chart shown in FIG. 6. To determine an occurrence of atachyarrhythmia, the ICD may first compare a detected heart rate to afirst heart rate threshold, as at 601. For example, the ICD may usereceived cardiac electrical signals, in some embodiments in conjunctionwith other received physiological signals, to determine a heart rate. Ifthe ICD determines that the heart rate is greater than or equal to thefirst heart rate threshold, the ICD may compare the morphology of thecardiac electrical signal of a current heart beat with the morphology ofa template of a normal heart beat, as at 603. For example, the ICD mayisolate a region of cardiac electrical activity surrounding a QRScomplex of a current heart beat and perform a correlation analysisbetween the morphology of the isolated QRS complex (or part thereof) andthe template containing a QRS complex (or part thereof) of a normalheart beat. If the correlation between the current beat and the templatebeat is greater than or equal to a first correlation threshold, the ICDmay determine that there is no tachyarrhythmia present, as at 605. Inthese cases, the heart rate may be elevated due to exercise or stress,or some other factor, rather than due to an abnormal physiologicalprocess.

If, however, the correlation between the current heart beat and thetemplate beat is not greater than or equal to the first correlationthreshold, the ICD may then compare the morphology of the current heartbeat with the morphology of one or more previous heart beats, as at 607.For example, the ICD may isolate the QRS complexes of the current heartbeat and the previous heart beat and perform a correlation analysisbetween the morphologies of the two beats. If the correlation betweenthe two beats is less than a second correlation threshold, the ICD maydetermine that the tachyarrhythmia is a polymorphic ventriculartachyarrhythmia (PVT), as at 609. However, if the correlation betweenthe two beats is greater than or equal to the second correlationthreshold, the ICD may further compare the width of the QRS complex ofthe current beat with the width of the QRS complex of the templatenormal beat, as at 611. For example, the ICD may compare the differencein QRS widths between the current beat and the template beat to a QRSwidth threshold. If the difference in QRS widths is greater than orequal to the QRS width threshold (indicating that the width of the QRScomplex of the current beat is wider than the width of the QRS complexof the template beat by a threshold amount), the ICD may determine thatthe tachyarrhythmia is a monomorphic ventricular tachyarrhythmia (MVT),as at 613. However, if the ICD determines that the difference in QRSwidths is less than the QRS width threshold (indicating that the widthof the QRS complex of the current beat is narrower than the width of theQRS complex of the template beat), the ICD may determine that thetachyarrhythmia is a supraventricular tachyarrhythmia (SVT), as at 615.

It should be noted that the flow chart of FIG. 6 is only one embodimentin which the ICD may determine occurrences and/or discriminate types oftachyarrhythmias. For instance, in some additional embodiments, the ICDmay further compare the determine heart rate to a second heart ratethreshold, where the second heart rate threshold is greater than thefirst heart rate threshold. If the heart rate is greater than or equalto the second heart rate threshold, the ICD may determine that the heartis in ventricular fibrillation (VF). Additionally, or alternatively, insome embodiments, the ICD may additionally use the width of the currentQRS complex and the width of the QRS complex of the template beat inperforming the correlation analysis between the current beat and thetemplate beat in step 607. Of course, in still other embodiments, theICD may use different methods for determining occurrences oftachyarrhythmias and discriminating between various types oftachyarrhythmias, which may include fewer or greater numbers of stepsthan those listed in FIG. 6.

Where the ICD discriminates between different types of tachyarrhythmias,the ICD may coordinate with LCP 402 to implement differing treatmentprotocols. For example, the ICD may have stored in memory a first set oftachyarrhythmia types. If the determined tachyarrhythmia is one of thetypes of tachyarrhythmias in the first set of tachyarrhythmia types, theICD may communicate an instruction to LCP 402 to initiate application ofATP therapy. In some cases, the ICD may also wait to initiate chargingof its charge storage device for delivery of defibrillation and/orcardioversion therapy. The ICD may then monitor the cardiac electricalsignals to determine if the ATP therapy delivered by LCP 402 terminatesthe tachyarrhythmia. If the ICD determines that the tachyarrhythmia wasnot terminated by the ATP, the ICD may initiate charging of its chargestorage device and deliver defibrillation and/or cardioversion therapyonce the charge is complete. In determining whether the delivery of ATPtherapy has terminated the tachyarrhythmia, the ICD may determine thecurrent heart rate and compare it to a threshold or compare it to theheart rate at the time the tachyarrhythmia was detected. If the heartrate is less than the comparison heart rate, the ICD may determine thatthe tachyarrhythmia was terminated. In other embodiments, the ICD mayperform the process detailed in FIG. 6 to determine if the ATP therapyterminated the tachyarrhythmia.

In embodiments where the types of tachyarrhythmias in the first set oftachyarrhythmia types are types that are likely to be susceptible to ATPtherapy, the ICD may conserve energy by waiting to charge its chargestorage device until after confirmation that the ATP therapy failed toterminate the tachyarrhythmia. In some embodiments, the types oftachyarrhythmia in the first set of tachyarrhythmia types may includeMVT. However, in other embodiments, PVT may also be included in thefirst set of tachyarrhythmia types. In still other embodiments, SVTand/or VF may also be included in the first set of tachyarrhythmiatypes. These are just examples.

In embodiments where the type of tachyarrhythmia is not one of thetachyarrhythmias in the first set of tachyarrhythmia types, the ICD maynot send the instruction to LCP 402 to initiate ATP therapy. Instead,the ICD may initiate charging of the charge storage device and deliverdefibrillation and/or cardioversion therapy once the charging iscomplete. In some embodiments, VF may be excluded from the first set oftachyarrhythmia types. In some embodiments, PVT and/or SVT may beexcluded from the first set of tachyarrhythmia types.

In some instances, the ICD may alter the treatment protocol based on thedetermined type of tachyarrhythmia. For instance, if the ICD determinesthat the tachyarrhythmia is one of the tachyarrhythmia types in thefirst set of tachyarrhythmia types, the ICD may send the instruction toLCP 402 to initiate ATP therapy but also begin charging its chargestorage device for delivery of defibrillation and/or cardioversiontherapy. This may best be applied when the determined type oftachyarrhythmia has some non-trivial chance that ATP therapy wouldterminate the tachyarrhythmia, but is still un-likely to be successful.The ICD may monitor the cardiac electrical activity while charging thecharge storage device and while LCP 402 is delivering ATP therapy. Ifdelivery of ATP therapy does actually terminate the tachyarrhythmia, theICD may terminate the charging of its charge storage device, and thensubsequently slowly leak off the accumulated charge without performingdefibrillation and/or cardioversion therapy. In such embodiments, theICD may save some energy by not unnecessarily fully charging its chargestorage device, and may also not harm or scare the patient by deliveringan unnecessary defibrillation and/or cardioversion pulse. If delivery ofATP therapy fails to terminate the tachyarrhythmia, the ICD may continueto fully charge the charge storage device and perform defibrillationand/or cardioversion therapy. In these embodiments, the ICD has savedtime between the detection of the tachyarrhythmia and the delivery ofthe defibrillation and/or cardioversion therapy by initiating chargingof its charge storage device earlier than if the determinedtachyarrhythmia was one of the first set of tachyarrhythmia types. Insome embodiments, the charge storage device may begin charging, withoutfirst waiting for ATP therapy, when the tachyarrhythmia is a PVT or SVTtype tachyarrhythmia. In other embodiments, the charge storage devicemay begin charging, without first waiting for ATP therapy, when thetachyarrhythmia is a MVT and/or VF.

In additional or alternative embodiments, the instruction sent to LCP402 to initiate ATP therapy may include one or more ATP parameters thatdefine one or more characteristics of the ATP therapy. For example, theinstruction may specify a number of ATP therapy attempts that are to beattempted by LCP 402 before terminating the ATP therapy protocol. Forinstance, if the tachyarrhythmia type is a first type oftachyarrhythmia, the ICD may communicate an instruction that LCP 402should attempt a defined ATP therapy two, or three, or five, or anyother suitable number of times. Each attempt may include applying aplurality of spaced ATP pulses to the heart. If the tachyarrhythmia typeis a second type of tachyarrhythmia, different and distinguishable fromthe first type of tachyarrhythmia, the ICD may communicate aninstruction that LCP 402 should only provide one ATP therapy attempt.For example, for MVT, ATP therapy may be applied in multiple bursts(sometimes as programmed by a clinician) and more time may be allowed toterminate the tachyarrhythmia given the higher chance of success for ATPtherapy when applied to MVT, whereas for other types of tachyarrhythmia(e.g. PVT, SVT and/or VF), it may be more appropriate to apply a singleburst (single ATP attempt) to help reduce the time to defibrillationand/or cardioversion therapy given the lower chance of success for ATPtherapy.

In some cases, the charge storage device of the ICD may be charged inparallel with the ATP therapy delivered by the LCP 402. In these cases,the instruction sent to LCP 402 may command LCP 402 to perform a numberof ATP therapy attempts that tend to fill up the time it takes the ICDto charge its charge storage device. In other instances, eachinstruction the ICD sends to LCP 402 commanding LCP 402 to perform ATPtherapy may instruct LCP 402 to perform a single ATP attempt. Then, ifthe ICD determines that the ATP attempt did not terminate the detectedtachyarrhythmia, the ICD may communicate an additional instruction toLCP 402 to perform another ATP attempt. In such instances, the resultmay be that the ICD may communicate a different number of instructionsfor delivery of ATP therapy, depending on whether the ATP therapy wassuccessful or not.

The instructions sent by the ICD to the LCP 402 commanding LCP 402 toperform ATP may define one or more characteristics of the ATP therapy.Example parameters may include a number of ATP bursts—e.g. ATP pulses—tobe delivered by LCP 402 during each ATP therapy attempt. This parametermay be in addition to the number of ATP therapy attempts or analternative. In some embodiments, the number of ATP pulses may bespecified differently for each ATP therapy attempt, where LCP 402 isinstructed to perform multiple ATP therapy attempts. Also, the number ofATP pulses may be specified differently depending on the determined typeof tachyarrhythmia. Additionally, in embodiments where the instructionto LCP 402 includes a number of ATP therapy attempts, the instructionsmay, in some embodiments, further include specific rates of ATP pulsedelivery during each ATP therapy attempt. As with the number of ATPpulses in each attempt, the rates of ATP pulse delivery may differbetween ATP therapy attempts and/or depending on the detectedtachyarrhythmia type. Additionally, or alternatively, the instructionsmay specify a length of a break period between ATP therapy attempts.Other example parameters may include a pulse amplitude and/or a pulsewidth of the ATP pulses to be delivered during each ATP therapy attempt.As with the other parameters, the instructions may specify differentamplitudes and/or pulse widths for each ATP therapy attempt and/or basedon the determined type of tachyarrhythmia.

The instructions sent by the ICD to the LCP 402 commanding LCP 402 toperform ATP may additionally, or alternatively, include an instructionto perform ATP according one of a number of methods. According to aburst method, LCP 402 may deliver consecutive electrical stimulationpulses with a constant time interval between each electrical stimulationpulse. Additionally, when delivering ATP according to the burst method,LCP 402 may deliver each sequence of electrical stimulation pulses witha constant time interval between each of the sequences of electricalstimulation pulses. In another method, the ramp method, LCP 402 maydeliver electrical stimulation pulses within a sequence of electricalstimulation pulses, or ATP therapy attempt, with a decreasing timeinterval between each pair of successive electrical stimulation pulses.In yet another method, the scan method, LCP 402 may deliver sequences ofelectrical stimulation pulses, or ATP therapy attempts, with a timeinterval between electrical stimulation pulses within each sequence ofelectrical stimulation pulses that decreases for each successivesequence of electrical stimulation pulses. In still another method, theramp/scan method, LCP 402 may deliver ATP therapy according to thefeatures of both the ramp method and the scan method.

In embodiments where the ICD includes an instruction to perform ATPaccording to specific method, the specific method may depend at leastpartially on the type of cardiac arrhythmia. For instance, if thearrhythmia is one of the first set of arrhythmia types, the ICD maycommunicate a message to LCP 402 to perform ATP therapy according to theburst method. However, if the arrhythmia type is one of the second setof arrhythmia types, the ICD may communicate a message to LCP 402 toperform ATP therapy according to the ramp method. Of course, in otherembodiments, the type of method associated with each arrhythmia type maydiffer and may be any of the burst, ramp, scan, or ramp/scan methods.

In some embodiments, the types of tachyarrhythmias in the first andsecond sets of tachyarrhythmia types may be user programmable. Forinstance, as described with respect to FIG. 4, the ICD, including pulsegenerator 406, may be able to communicate with external support device420, which in some embodiments may act as a programmer. A clinician mayinteract with the programmer to specify which tachyarrhythmias types areto be included in each of the first and second sets of tachyarrhythmiatypes, and which tachyarrhythmia types are not in either set. In somecases, the first set of cardiac arrhythmia types and the second set ofcardiac arrhythmia types may be the same cardiac arrhythmia types. Inother cases, the first set of cardiac arrhythmia types and the secondset of cardiac arrhythmia types may be mutually exclusive. In othercases, the first set of cardiac arrhythmia types and the second set ofcardiac arrhythmia types may share one or more common cardiac arrhythmiatypes.

In some embodiments, the types of tachyarrhythmias in the first andsecond sets of tachyarrhythmia types may depend at least partially onthe level of charge in the energy storage module that powers the ICD.For example, the ICD may determine a percentage of remaining energycapacity of energy storage module 218. The ICD may begin with, forexample, MVT and PVT in the first set of tachyarrhythmia types, and PVTin the second set of tachyarrhythmia types. That is, if either MVT orPVT is detected, the ICD may send an instruction to the LCP 402 toinitiate the application of ATP therapy by the LCP 402. If PVT isdetected, the ICD may initiate charging of the charge storage device,and if MVT is detected, the ICD may wait on initiating charging of thecharge storage device until ATP is given a chance to terminate thetachyarrhythmia. Once the ICD determines that the percentage of capacityof remaining energy storage module 218 has dropped below, for example,fifty percent, the ICD may recommend and/or automatically remove PVTfrom the first set of tachyarrhythmia types. Then, if the ICD detectsPVT, the ICD may not send an instruction to the LCP 402 to initiate theapplication of ATP therapy by the LCP 402. Removing PVT from the firstset of tachyarrhythmia types may help increase the remaining life of thebattery of the ICD by not performing ATP therapy in cases wherein ATPtherapy is less likely to be successful (e.g. PVT verses MVT). This isjust one example. In other embodiments, different types oftachyarrhythmias may be moved, added or deleted from each of the sets.In some cases, one or more thresholds may be used for adjusting whichtachyarrhythmia types are in each set of tachyarrhythmia types.

FIG. 7 is a flow diagram of an illustrative method 700 that may beimplemented by a medical device, such as that shown in FIG. 2, which insome embodiments may be an ICD. Although the method of FIG. 7 will bedescribed with respect to MD 200, the illustrative method of FIG. 7 maybe performed by any suitable medical device or medical device system.

In some embodiments, MD 200 may determine an occurrence of a cardiacarrhythmia, as shown at 701. In some cases, MD 200 may determine anoccurrence of a cardiac arrhythmia, and specifically a tachyarrhythmia,according to the flow diagram of FIG. 6. However, in other embodiments,MD 200 may use additional or alternative techniques to determine anoccurrence of a cardiac arrhythmia. After determining an occurrence of acardiac arrhythmia, MD 200 may determine a type of the detected cardiacarrhythmia from two or more types of cardiac arrhythmias, as shown at703. For example, MD 200 may discriminate between two or more differentcardiac arrhythmias types. In embodiments where MD 200 discriminatesbetween different types of tachyarrhythmias, MD 200 may operateaccording to a method detailed in FIG. 6. However, in other embodiments,MD 200 may operate differently than described with respect to FIG. 6 todiscriminate between tachyarrhythmia types.

After determining a type of cardiac arrhythmia, MD 200 may, if thedetermined type of cardiac arrhythmia is one of a first set of cardiacarrhythmia types, send an instruction for reception by a LeadlessCardiac Pacemaker (LCP) to initiate the application of ATP therapy bythe LCP, as shown at 705. In some embodiments, the instruction mayinclude one or more parameters that define a characteristic of the ATPtherapy. Some example parameters include a number of ATP therapyattempts, a number of ATP bursts in each ATP therapy attempt, a lengthof a break between ATP therapy attempts, an amplitude and/or pulse widthof each ATP burst, among other parameters. If the determined type ofcardiac arrhythmia is not one of the first set of cardiac arrhythmiatypes, MD 200 may not send the instruction to the LCP, as shown at 707.

In some additional or alternative embodiments, MD 200 may further begincharging a charge storage device (for instance, a charge storage devicethat may be a part of pulse generator module 204) if the determined typeof the cardiac arrhythmia is one of a second set of cardiac arrhythmiatypes in addition to sending the instruction. However, if the determinedtype of tachyarrhythmia is not one of the second set of cardiacarrhythmia types, MD 200 may wait to charge the charge storage deviceuntil after confirming that the delivered ATP therapy failed toterminate the tachyarrhythmia.

FIG. 8 is a flow diagram of an illustrative method 800 that may beimplemented by a medical device, such as that shown in FIG. 2, which insome embodiments may be an ICD. Although the method of FIG. 8 will bedescribed with respect to MD 200, the illustrative method of FIG. 8 maybe performed by any suitable medical device or medical device system.

In some embodiments, MD 200 may determine an occurrence of a cardiacarrhythmia, as shown at 801. In some cases, MD 200 may determine anoccurrence of a cardiac arrhythmia, and specifically a tachyarrhythmia,according to the flow diagram of FIG. 6. However, in other embodiments,MD 200 may use additional or alternative techniques to determine anoccurrence of a cardiac arrhythmia. After determining an occurrence of acardiac arrhythmia, MD 200 send an instruction for reception by aLeadless Cardiac Pacemaker (LCP) to initiate application of ATP therapy,as at 803.

After sending the instruction, MD 200 may determine a type of thedetected cardiac arrhythmia from two or more types of cardiacarrhythmias, as shown at 805. For example, MD 200 may discriminatebetween two or more different cardiac arrhythmias types. In embodimentswhere MD 200 discriminates between different types of tachyarrhythmias,MD 200 may operate according to a method detailed in FIG. 6. However, inother embodiments, MD 200 may operate differently than described withrespect to FIG. 6 to discriminate between tachyarrhythmia types.

After determining a type of cardiac arrhythmia, MD 200 may, if thedetermined type of cardiac arrhythmia is one of a first set of cardiacarrhythmia types, wait to initiate charging of its charge storagedevice, as shown at 807. For instance, MD 200 may monitor receivedelectrical cardiac signals during and after delivery of ATP therapy bythe LCP. In these embodiments, MD 200 may attempt to save battery energyby waiting until confirming that the delivery of ATP therapy did notterminate the tachycardia. Once MD 200 has confirmed that delivery ofATP therapy has failed to terminate the tachycardia, MD 200 may initiatecharging of its charge storage device for delivery of defibrillationand/or cardioversion therapy. In instances where delivery of ATP therapydid terminate the tachycardia, MD 200 has saved energy by not chargingits charge storage device.

However, if the determine type of cardiac arrhythmia is not one of thefirst set of cardiac arrhythmia types, MD 200 may initiate charging ofits charge storage device, as shown at 809. In some embodiments, whilecharging its charge storage device, MD 200 may monitor received cardiacelectrical signals. MD 200 may determine, based at least in part on thereceived signals, whether delivery of ATP therapy by the LCP hasterminated the tachycardia. If MD 200 determines that the delivery ofATP therapy has terminated the tachycardia, MD 200 may cease chargingits charge storage device. MD 200 may then slowly leak off theaccumulated charge. However, if MD 200 determines that the delivery ofATP therapy has not terminated the tachycardia, MD 200 may deliverdefibrillation and/or cardioversion therapy once charging of its chargestorage device is complete.

The above description of determining occurrences of tachyarrhythmias anddiscriminating between the various tachyarrhythmia types used a systemincluding an ICD/SICD and an LCP as an example only. In otherembodiments, other devices may be used as part of the systemimplementing the disclosed techniques. In still other embodiments, asystem implementing the disclosed techniques may include additionaldevices. In such embodiments, determining occurrences oftachyarrhythmias, discriminating between the different types oftachyarrhythmias, communicating instructions, delivering ATP therapy,and/or delivering defibrillation/cardioversion therapy may becoordinated between the devices, as desired.

Those skilled in the art will recognize that the present disclosure maybe manifested in a variety of forms other than the specific embodimentsdescribed and contemplated herein. For instance, as described herein,various embodiments include one or more modules described as performingvarious functions. However, other embodiments may include additionalmodules that split the described functions up over more modules thanthat described herein. Additionally, other embodiments may consolidatethe described functions into fewer modules. Accordingly, departure inform and detail may be made without departing from the scope and spiritof the present disclosure as described in the appended claims.

What is claimed is:
 1. A subcutaneous implantable cardioverterdefibrillator (SICD) for delivering a defibrillation shock to a heart ofa patient, the SICD comprising: two or more electrodes; a charge storagedevice for storing a charge that can be delivered to shock the heart viatwo or more of the electrodes; a controller operatively coupled to twoor more of the electrodes and the charge storage device, the controllerconfigured to: monitor cardiac activity of the heart of the patient viacardiac signals received via two or more of the electrodes; detect anoccurrence of a cardiac arrhythmia based on the cardiac activity;determine a type of the detected cardiac arrhythmia from two or moretypes of cardiac arrhythmias; in response to finding that the determinedtype of cardiac arrhythmia is one of a first set of cardiac arrhythmiatypes, sending an instruction via two or more of the electrodes forreception by a Leadless Cardiac Pacemaker (LCP) to initiate theapplication of Anti-Tachycardia Pacing (ATP) therapy by the LCP; inresponse to finding that the determined type of cardiac arrhythmia isnot one of the first set of cardiac arrhythmia types, not sending theinstruction; in response to finding that the determined type of thecardiac arrhythmia is one of a second set of cardiac arrhythmia types,initiate charging of the charge storage device; in response to findingthat the determined type of the cardiac arrhythmia is not one of thesecond set of cardiac arrhythmia types, waiting to initiate charging ofthe charge storage device; and wherein when an instruction was sent toinitiate the application of ATP therapy by the LCP, the controller isfurther configured to determine when the application of the ATP therapyby the LCP was successful in terminating the cardiac arrhythmia, andwhen the application of the ATP therapy by the LCP was successful, notinitiating charging of the charge storage device when the determinedtype of the cardiac arrhythmia is not one of the second set of cardiacarrhythmia types.
 2. The SICD of claim 1, wherein the instruction alsoincludes one or more ATP parameters that define one or morecharacteristics of the ATP therapy.
 3. The SICD of claim 2, wherein theone or more characteristics of the ATP therapy comprise a method of ATPtherapy.
 4. The SICD of claim 1, wherein when an instruction was sent toinitiate the application of ATP therapy by the LCP, the controller isfurther configured to determine when the application of the ATP therapyby the LCP was successful in terminating the cardiac arrhythmia, andwhen the application of the ATP therapy by the LCP was successful,terminating the charging of the charge storage device when thedetermined type of the cardiac arrhythmia is one of the second set ofcardiac arrhythmia types.
 5. An implantable cardioverter defibrillator(ICD) for delivering a defibrillation shock to a heart of a patient, theICD comprising: a charge storage device for storing a charge that can bedelivered to shock the heart; a controller operatively coupled to thecharge storage device, the controller configured to: monitor cardiacactivity of the heart of the patient; detect an occurrence of a cardiacarrhythmia based on the cardiac activity; determine a type of thedetected cardiac arrhythmia from two or more types of cardiacarrhythmias; in response to finding that the determined type of cardiacarrhythmia is one of a first set of cardiac arrhythmia types, sending aninstruction for reception by a Leadless Cardiac Pacemaker (LCP) toinitiate the application of Anti-Tachycardia Pacing (ATP) therapy by theLCP; in response to finding that the determined type of cardiacarrhythmia is not one of the first set of cardiac arrhythmia types, notsending the instruction; in response to finding that the determined typeof the cardiac arrhythmia is one of a second set of cardiac arrhythmiatypes, initiate charging of the charge storage device; in response tofinding that the determined type of the cardiac arrhythmia is not one ofthe second set of cardiac arrhythmia types, waiting to initiate chargingof the charge storage device; and wherein when an instruction was sentto initiate the application of ATP therapy by the LCP, the controller isfurther configured to determine when the application of the ATP therapyby the LCP was successful in terminating the cardiac arrhythmia, andwhen the application of the ATP therapy by the LCP was successful, notinitiating charging of the charge storage device when the determinedtype of the cardiac arrhythmia is not one of the second set of cardiacarrhythmia types.
 6. The ICD of claim 5, wherein the instructionincludes one or more ATP parameters that define one or morecharacteristics of the ATP therapy.
 7. The ICD of claim 6, wherein theone or more characteristics of the ATP therapy comprise a method of ATPtherapy.
 8. The ICD of claim 5, wherein when an instruction was sent toinitiate the application of ATP therapy by the LCP, the controller isfurther configured to determine when the application of the ATP therapyby the LCP was successful in terminating the cardiac arrhythmia, andwhen the application of the ATP therapy by the LCP was successful,terminating the charging of the charge storage device when thedetermined type of the cardiac arrhythmia is one of the second set ofcardiac arrhythmia types.
 9. A method implemented by an implantablecardioverter defibrillator (ICD), the method comprising: determining anoccurrence of a cardiac arrhythmia; determining a type of the detectedcardiac arrhythmia from two or more types of cardiac arrhythmias; inresponse to finding that the determined type of cardiac arrhythmia isone of a first set of cardiac arrhythmia types, sending an instructionfor reception by a Leadless Cardiac Pacemaker (LCP) to initiate theapplication of Anti-Tachycardia Pacing (ATP) therapy by the LCP; and inresponse to finding that the determined type of cardiac arrhythmia isnot one of the first set of cardiac arrhythmia types, not sending theinstruction to the LCP.
 10. The method of claim 9 further comprises: inresponse to finding that the determined type of the cardiac arrhythmiais one of a second set of cardiac arrhythmia types, charging the chargestorage device; and in response to finding that the determined type ofthe cardiac arrhythmia is not one of the second set of cardiacarrhythmia types, waiting to charge the charge storage device.